Integrated circuit including single crystal semiconductor layer on non-crystalline layer

ABSTRACT

A method of forming a single crystal semiconductor film on a non-crystalline surface is described. In accordance with this method, a template layer incorporating an ordered array of nucleation sites is deposited on the non-crystalline surface, and the single crystal semiconductor film is formed on the non-crystalline surface from the ordered array of nucleation sites. An integrated circuit incorporating one or more single crystal semiconductor layers formed by this method also is described.

TECHNICAL FIELD

[0001] This invention relates to systems and methods for forming asingle crystal semiconductor film on a non-crystalline (e.g., anamorphous) surface.

BACKGROUND

[0002] Many different methods have been developed for forming singlecrystal epitaxial semiconductor films. Epitaxy is the regularly orientedgrowth of a crystalline substance on a crystalline surface. Singlecrystal films frequently have superior properties relative to otherkinds of films, such as polycrystalline and amorphous films. Homoepitaxyis the growth of a crystalline film on a crystalline surface of the samesubstance. Heteroepitaxy is the growth of a crystalline film on acrystalline surface of a different substance. Chemical vapor deposition(CVD) processes, and to a lesser extent, physical vapor depositionprocesses, commonly are used to grow or deposit single crystalsemiconductor layers on a crystalline substrate. The quality of thesingle crystal epitaxial films depends upon a number of differentfactors, including good lattice match between the film and thesubstrate, proper growth temperature, and proper reactantconcentrations.

[0003] For many applications, polycrystalline or amorphous films areacceptable or even more desirable than epitaxial films. For example,many protective films are polycrystalline films, which may becharacterized by high hardness, high corrosion resistance, and highoxidation resistance. Amorphous films (e.g., oxides, nitrides andglasses, such as silicon dioxide) also serve a number of usefulfunctions, including electronic passivation, insulation and dielectricfunctions. Current device performance requirements, however, requirethat most or all of the active devices of an integrated circuit beformed in a single crystal semiconductor region. This requirementtypically limits the integrated circuit devices to two-dimensionalstructures on a substrate surface.

[0004] Numerous attempts have been made to extend semiconductor devicefabrication techniques to three-dimensional structures by growing singlecrystal films over amorphous films used as insulators in two-dimensionalintegrated circuits. For example, U.S. Pat. No. 4,686,758 describes alocalized overgrowth process, in which seeding from a single crystalsilicon substrate is used to grow single crystal silicon layers over anamorphous silicon dioxide gate layer. The localized overgrowth processinvolves etching a window in the silicon dioxide layer down to thesingle crystal silicon substrate, and growing an epitaxial silicon filmupwardly from the substrate in the window. Localized overgrowth ofsingle crystal silicon occurs when the selective epitaxial growthreaches the top surface of the silicon dioxide window. U.S. Pat. No.6,103,019 describes a method of forming a single crystal film from aseed layer implanted in a non-crystalline surface by high-doseimplanting of a nucleating species through a single crystal mask havingappropriate channeling directions spaced at desired lattice constants.In zone melting recrystallization processes, a single crystalsemiconductor layer may be formed on an amorphous layer by depositing apolycrystalline or amorphous semiconductor layer, melting the depositedlayer with a laser or other energy source, and allowing the melted layerto re-crystallize, randomly or from a seed, by superposing a temperaturegradient. Still other single crystal forming processes have beenproposed.

SUMMARY

[0005] The invention features a novel single crystal semiconductor filmformation method in which a template layer is deposited onto anon-crystalline surface to serve as a seed layer for the subsequentepitaial growth of a single crystal semiconductor film.

[0006] In one aspect, the invention features a method of forming asingle crystal semiconductor film on a non-crystalline surface. Inaccordance with this inventive method, a template layer incorporating anordered array of nucleation sites is deposited on the non-crystallinesurface, and the single crystal semiconductor film is formed on thenon-crystalline surface from the ordered array of nucleation sites.

[0007] As used herein, the phrase “forming a single crystalsemiconductor film from an ordered array of nucleation sites” refersbroadly to the transfer of ordering information from the nucleationsites to the single crystal film being deposited.

[0008] Embodiments of the invention may include one or more of thefollowing features.

[0009] The template layer preferably comprises an ordered array oforganic molecules. The organic molecules may incorporate an inorganicspecies defining the ordered array of nucleation sites. The inorganicspecies may comprise one or more components of the single crystalsemiconductor film. In some embodiments, the template layer is aLangmuir-Blodgett film. In one embodiment, the template layer comprisesa close-packed matrix of polymerized organic monomers each incorporatingone or more silicon atoms, and the single crystal semiconductor film isan epitaxial silicon film.

[0010] The template layer may include one or more monolayers depositedon the non-crystalline surface. The deposited template layer may beprocessed to expose the ordered array of nucleation sites. The templatelayer may be processed, e.g., by heating, to remove one or more volatilecomponents of the template layer.

[0011] The template layer may deposited by a Langmuir-Blodgettdeposition process, or by an evaporation-based deposition process.

[0012] The single crystal semiconductor film may be formed by a vaporphase deposition process, a solid-state crystallization process, or azone melting recrystallization process.

[0013] A non-crystalline layer may be formed over the single crystalsemiconductor film, and a second template layer incorporating an orderedarray of nucleation sites may be deposited on the non-crystalline laver.A second single crystal semiconductor film may be formed from theordered array of nucleation sites of the second template layer.

[0014] In another aspect, the invention features an integrated circuit,comprising a single crystal semiconductor layer formed from an orderedarray of nucleation sites defined by an array of organic moleculesdisposed over a non-crystalline layer.

[0015] Among the advantages of the invention are the following.

[0016] The invention provides a method of forming single crystalsemiconductor films of any desired orientation on an amorphous layer.This feature enables high quality, vertically integrated semiconductordevices (e.g., complementary metal-oxide semiconductor (CMOS) devices)to be fabricated. The invention therefore provides an alternativeprocess for developing high density and high performancethree-dimensional integrated circuits. In addition, the inventionenables large area single crystal semiconductor films to be grown onamorphous glass substrates that may be used to produce, for example,high efficiency solar cells or components of displays.

[0017] Other features and advantages of the invention will becomeapparent from the following description, including the drawings and theclaims.

DESCRIPTION OF DRAWINGS

[0018]FIG. 1 is a flow diagram of a method of forming a single crystalsemiconductor film on a non-crystalline surface.

[0019]FIG. 2A is a diagramatic cross-sectional side view of a templatelayer deposited on a non-crystalline surface.

[0020]FIG. 2B is a diagrammatic cross-sectional side view of thetemplate layer of FIG. 2A after being processed to expose an orderedarray of nucleation sites on the non-crystalline surface of FIG. 2A.

[0021]FIG. 2C is a diagrammatic cross-sectional side view of an incomingvapor phase species condensing at preferred bonding sites defined by theordered array of nucleation sites formed on the non-crystalline surfaceof FIG. 2A.

[0022]FIG. 2D is a diagrammatic cross-sectional side view of a monolayerof a single crystal semiconductor film formed on the non-crystallinesurface of FIG. 2A.

[0023]FIG. 2E is a diagrammatic cross-sectional side view of a pluralityof monolayers of a single crystal semiconductor film formed on thenon-crystalline surface of FIG. 2A.

[0024]FIG. 3 is a diagrammatic cross-sectional side view of a singlecrystal semiconductor film formed on a non-crystalline passivation layerof an integrated circuit.

DETAILED DESCRIPTION

[0025] In the following description, like reference numbers are used toidentify like elements. Furthermore, the drawings are intended toillustrate major features of exemplary embodiments in a diagrammaticmanner. The drawings are not intended to depict every feature of actualembodiments or relative dimensions of the depicted elements, and are notdrawn to scale.

[0026] Referring to FIGS. 1 and 2-2E, a single crystal semiconductorfilm may be formed on a non-crystalline surface as follows. A templatelayer 10 incorporating an ordered array of nucleation sites 12 isdeposited on a non-crystalline surface 14 (step 16). A single crystalsemiconductor film 18 is formed on non-crystalline surface 14 from theordered array of nucleation sites 12 (step 24). In some embodiments, thetemplate layer 10 may be processed to expose the ordered array ofnucleation sites 12 before the single crystal semiconductor film 18 isformed (step 28).

[0027] Referring to FIG. 2A, template layer 10 may be deposited onnon-crystalline surface 14 in a number of different ways.

[0028] In one template layer deposition embodiment, template layer 10 isa Langinuir-Blodgett film formed from an ordered array (or matrix) oforganic molecules. Template layer 10 may be formed by layering asuitable matrix-forming material onto a formation support. The formationsupport may be a standard Langmuir-Blodgett trough containing an aqueoussolution and one or more movable barriers. The matrix-forming materialmay be layered onto the surface of the aqueous solution and compressedby the one or more movable barriers to form a tight-packed monolayer ofthe matrix-forming material. In some embodiments, the matrix-formingmaterial may be polymerized by irradiation (e.g., ultravioletirradiation, gamma irradiation, x-ray irradiation, and electron beamexposure). Template layer 10 is deposited onto) non-crystalline surface14 from the aqueous solution inside the Langmuir-Blodgett trough. Insome embodiments, a substrate carrying the non-crystalline surface 14 isimmersed vertically into the aqueous solution inside theLangmuir-Blodgett trough. As the substrate is withdrawn from theLangmuir-Blodgett trough, a monolayer of the matrix-forming material isdeposited onto non-crystalline surface 14 to form template layer 10. Thematrix-forming material may be removed from other portions of thesubstrate (e.g., the backside of the substrate) by applying a suitablesolvent. In other embodiments, the substrate may be immersedhorizontally into the Langmuir-Blodgett trough with non-crystallinesurface 14 exposed for contact with the matrix-forming materialsupported on the aqueous solution contained in the Langmuir-Blodgetttrough.

[0029] In another template layer deposition embodiment, a suitablematrix-forming material may be deposited directly onto non-crystallinesurface 14. For example, the matrix-forming material may be evaporatedand condensed onto non-crystalline surface 14. Non-crystalline surface14 may be heated so that the matrix-forming material remainssufficiently fluid to self-assemble (or polymerize) into a close-packedmonolayer of ordered matrix-forming molecules on non-crystalline surface14.

[0030] As shown in FIG. 2B, in some embodiments, template layer 10 maybe processed to expose an ordered array of nucleation sites 12 acrossnon-crystalline surface 14. For example, template layer 10 may be heatedto drive off one or more volatile components of the matrix-formingmaterial. The components of template layer 10 remaining onnon-crystalline surface 14 define the ordered array of nucleation sites12. In other embodiments, the single crystal semiconductor layer may beformed directly on template layer 10 without any post-depositionprocessing.

[0031] Single crystal semiconductor layer 18 may be formed from theordered array of nucleation sites 12 using many different film growthprocesses, including vapor phase deposition (e.g., chemical vapordeposition and molecular beam epitaxy), liquid phase crystallization(e.g., liquid phase epitaxy and zone melting recrystallization) andsolid-state crystallization techniques.

[0032] Referring to FIGS. 2C and 2D, in a vapor phase crystallizationprocess, a suitable vaporized semiconductor species 3) is introducedinto the space above the ordered array of nucleation sites 12 onnon-crystalline surface 14. The ordered array of nucleation sites 12defines an array of low-energy (or otherwise preferred) bonding sitesfor the constituent components of single crystal semiconductor layer 18and, therefore, serves as a suitable seed layer for the growth of asingle crystal semiconductor film. The substrate supporting thenon-crystalline surface 14 may be heated. Thermal energy from the heatedsubstrate allows the semiconductor molecules from the incoming speciesto migrate on the non-crystalline surface 14 to the slow energy bondingsites formed by the chemically applied template layer 10. Duringdeposition of single crystal semiconductor layer 18, the incomingsemiconductor molecules 30 initially form a plurality of nuclei at thelow energy bonding sites on non-crystal line surface 14. The low-energybonding sites defined by nucleation sites 12 preferably are spaced-apartby a distance substantially corresponding to the lattice constant or amultiple of the lattice constant characteristic of the single crystalsemiconductor layer 18. The practical range of mismatch between thepreferred bonding site spacing and the lattice constant of the singlecrystal semiconductor film depends upon a number of factors, includingthe level of elastic strain in single crystal semiconductor film 18 andthe acceptable density of misfit dislocations in the single crystalsemiconductor film 18.

[0033] As shown in FIG. 2E, additional epitaxial semiconductor layersmay be grown on top of the initial layer. If the bonding site spacingmatches the lattice constant of the single crystal semiconductor film18, film 18 may be grown to any desired thickness. On the other hand, ifthere is some mis-match between the bonding site spacing and the latticeconstant of the single crystal semiconductor film 18, the thickness offilm 18 may be limited by the build-up of elastic strain, which resultsfrom the altered lattice constant of the initial layers of film 18 thataccommodate the bonding site spacing mismatch. In general, the greaterthe mismatch, the thinner film 18 may be made before the elastic strainis relieved by misfit dislocation formation.

EXAMPLE 1

[0034] Template layer 10 may serve as a seed layer for a single crystalelemental semiconductor film. For example, template layer 10 may serveas a seed layer for a single crystal silicon film having a (111)crystallographic orientation. The single crystal silicon film may begrown on a non-crystalline surface (e.g., an amorphous silicon dioxidelayer, an amorphous silicon nitride layer or an amorphous glasssubstrate). Template layer 10 may include a Langmuir-Blodgett filmformed from organic molecules that incorporate one or more silicon atomsand that, when polymerized, form a hexagonal close-packed film with aspacing between silicon atoms that matches the lattice constant of asingle crystal silicon film. A variety of different molecules may beused to form the Langmuir-Blodgett film, including n-dodecanoic acid(lauric acid), eicosanoic acid, ethyl stearate, eruric acid, brassidicacid, cyanine and hemicyanine dyes, porphyrin, and phthalocyanine.

[0035] Referring to FIG. 3, in accordance with this Example, templatelayer 10 may enable a single crystal silicon film 18 to be formed on atop surface 14 of a non-crystalline amorphous silicon dioxidepassivation layer 32 for an integrated circuit 34. Single crystalsilicon film 18 may be grown over the entire passivation layer 32 oronly over selected regions of passivation layer 32. For example, singlecrystal silicon film 18 may extend only over an area needed to fabricateone or more semiconductor devices. In some embodiments, single crystalsilicon film 18 may be used as a substrate for a second integratedcircuit. In these embodiments, a second amorphous insulating layer maybe formed above the single crystal silicon film 18, and a second singlecrystal silicon film may be formed on the second amorphous insulatinglayer. Multiple integrated circuit layers may be formed by growingadditional single crystal films on each subsequent amorphous insulatinglayer. This technique may be used to form high density three-dimensionalintegrated circuit structures.

EXAMPLE 2

[0036] Template layer 10 may serve as a seed layer for a compoundsemiconductor film. For example, template layer 10 may serve as a seedlayer for a single crystal gallium arsenide film grown on anon-crystalline surface (e.g., an amorphous silicon dioxide layer, anamorphous silicon nitride layer or an amorphous glass substrate).Template layer 10 may include a Langmuir-Blodgett film formed fromorganic molecules that incorporate gallium and arsenic atoms and that,when polymerized, form a close-packed film with appropriate respectivespacing between the gallium atoms and the arsenic atoms that match thegallium and arsenic pacing in a single crystal gallium arsenide film. Avariety of different molecules may be used to form the Langmuir-Blodgettfilm, including n-dodecanoic acid (lauric acid), eicosanoic acid, ethylstearate, eruric acid, brassidic acid, cyanine and hernicyanine dyes,porphyrin, and phthalocyanine.

[0037] In the above-described Examples, the template layers incorporatethe atoms found in the single crystal semiconductor films to be grown.In other embodiments, the template layers may incorporate atoms that aredifferent from the atoms of the single crystal semiconductor films.general, the incorporated atom spacing should substantially match thelattice constant (or a multiple of the lattice constant) of the singlecrystal semiconductor film The incorporated atoms also should bechemically compatible with the depositing species so that the depositingatoms of the single crystal semiconductor film may orient in properrelation to the ordered array of nucleation sites defined by theincorporated atoms. In addition, the atoms incorporated into thetemplate layer should not interfere with the growth of the singlecrystal semiconductor film (e.g., they should not promote decompositionof the incoming film-forming species, unless desired), nor should theyadversely affect the physical or electronic properties of thesubsequently formed single crystal semiconductor film.

[0038] Other embodiments are within the scope of the claims.

What is claimed is:
 1. A method of forming a single crystalsemiconductor film on a non-crystalline surface, comprising: depositingon the non-crystalline surface a template layer incorporating an orderedarray of nucleation sites; and forming the single crystal semiconductorfilm on the non-crystalline surface from the ordered array of nucleationsites.
 2. The method of claim 1, wherein the template layer comprises anordered array of organic molecules.
 3. The method of claim 2, whereinthe organic molecules incorporate an inorganic species defining theordered array of nucleation sites.
 4. The method of claim 3, wherein theinorganic species comprises one or more components of the single crystalsemiconductor film
 5. The method of claim 1, wherein the template layeris a Langmuir-Blodgett film.
 6. The method of claim 1, wherein thetemplate layer comprises a close-packed matrix of polymerized organicmonomers each incorporating one or more silicon atoms, and the singlecrystal semiconductor film is an epitaxial silicon film.
 7. The methodof claim 1, wherein the template layer comprises one or more monolayers.8. The method of claim 1, further comprising processing the depositedtemplate layer to expose the ordered array of nucleation sites.
 9. Themethod of claim 8, wherein the template layer is processed by removingone or more volatile components of the template layer.
 10. The method ofclaim 8, wherein the template layer is processed by heating.
 11. Themethod of claim 1, wherein the template layer is deposited by aLangmuir-Blodgett deposition process.
 12. The method of claim 1, whereinthe template layer is deposited by an evaporation-based depositionprocess.
 13. The method of claim 1, wherein the single crystalsemiconductor film is formed by a vapor phase deposition process. 14.The method of claim 1, wherein the single crystal semiconductor film isformed by a solid-state crystallization process.
 15. The method of claim1, wherein the single crystal semiconductor film is formed by a zonemelting recrystallization process.
 16. The method of claim 1, furthercomprising forming a non-crystalline layer over the single crystalsemiconductor film, and depositing on the non-crystalline layer a secondtemplate layer incorporating an ordered array of nucleation sites, andforming a second single crystal semiconductor film from the orderedarray of nucleation sites of the second template layer.
 17. A method offorming a single crystal semiconductor film on a non-crystallinesurface, comprising: depositing on the non-crystalline surface atemplate layer comprising a Langmuir-Blodgett film incorporating aninorganic species defining an ordered array of nucleation sites,processing the template layer to expose the ordered array of nucleationsites; and forming the single crystal semiconductor film on thenon-crystalline surface from the ordered array of nucleation sites. 18.The method of claim 17, wherein the template layer is deposited on thenon-crystalline surface by a Langmuir-Blodgett deposition process. 19.The method of claim 17, wherein the template layer is deposited on thenon-crystalline surface by an evaporation-based deposition process. 20.An integrated circuit, comprising a single crystal semiconductor layerformed from an ordered array of nucleation sites defined by an array oforganic molecules disposed over a non-crystalline layer.